<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>4</title>
</head>
<body>
<!--const声明 声明时必须赋值-->
    <script>
        const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
        // arr=[2,4,5,6,7,8,9]; error
    </script>
</body>
</html>